1. Field of the Invention
The present invention relates to the manufacturing method of a storage medium for collectively copying prescribed information from an electro-magnetic field copy master to a perpendicular magnetic record or vertical storage medium.
2. Description of the Related Art
Conventionally, as a method for manufacturing a vertical storage medium by magnetically copying prescribed information to it collectively, for example, a method for magnetically copying prescribed information to a vertical storage medium 183 by closely touching the vertical storage medium 183 on a magnetic copy master 182 provided with a Ni substrate 180 having concavity and convexity on the surface and a soft magnetic material 181 provided on the concavity and convexity of the Ni substrate 180, as shown in FIGS. 1 and 2, and externally applying a magnetic field to the recording surface of the vertical storage medium in the vertical direction is proposed (for example, see Patent reference 1).
In order to obtain good recording performance in such a vertical storage medium manufacturing method, magnetic flux must be collected on the convex part of the soft magnetic material 181 to increase a magnetic field in the neighborhood of the surface of the convex part of the soft magnetic material 181.
However, in the magnetic copy master 182 shown in FIG. 1, since a diamagnetic field is generated in a direction that is the reverse of the magnetic flux inside the soft magnetic material 181, leakage magnetic flux sufficiently large to contribute to the recording of the prescribed information cannot be obtained in the neighborhood of the surface of the soft magnetic material 181 because of this diamagnetic field. In the magnetic copy master 182 shown in FIG. 1, since the soft magnetic material 181 is provided on the concave and convex wall of the Ni substrate 180, as shown in FIG. 2, magnetic flux is easily collected on the edge of the convex part of the Ni substrate 180 to increase the magnetic field on the edge of the convex part of the soft magnetic material 181. Therefore, the reproduction waveform of the vertical storage medium 183 on which the prescribed information is recorded by this magnetic copy master 182 does not form a rectangular wave corresponding to the concavity and convexity of the Ni substrate 180 in the reproduction waveform 184 shown in FIG. 2.
In this case, it can be considered to increase an external magnetic field in order to obtain a magnetic field sufficiently large to contribute to the recording of the prescribed information at least in the neighborhood of the surface of the soft magnetic material 181. However, if an external magnetic field is large, for example, as shown in FIG. 3, the range of magnetic flux expands to the concave part of the Ni substrate 180 and the position of the magnetic wall (boundary where a magnetic field distributed inside the vertical storage medium 183 is inverted) of the vertical storage medium 183 does not coincide with the position of the edge of the concavity and convexity of the Ni substrate 180. Therefore, the reproduction waveform of the vertical storage medium 183 does not form a rectangular wave corresponding to the concavity and convexity of the Ni substrate 180.
If the reproduction waveform of the vertical storage medium 183 does not form a rectangular wave corresponding to the concavity and convexity of the Ni substrate 180 in this way, for example, the decoding of an address recorded in the vertical storage medium 183 and the demodulation accuracy of servo information degrades.
Thus, as the manufacturing method of a vertical storage medium for solving this problem, for example, as shown in FIG. 4, a method for magnetically copy the prescribed information to the vertical storage medium 183 collectively by closely touching the vertical storage medium 183 on a magnetic copy master 187 provided with a substrate 185 with concavity and convexity corresponding to the prescribed information on the surface and a strong magnetic material 186 provided in the concave part of the substrate 185 as shown in FIG. 4 and externally applying a magnetic field (arrow mark) to the recording surface of the vertical storage medium 183 in the horizontal direction issued (for example, see Patent reference 2).
In this manufacturing method of a vertical storage medium, as shown in FIG. 4, magnetic intensity 188 distributed in the vertical storage medium 183 is maximized on the edge of the strong magnetic material 186 and is reduced to almost zero around the center of each strong magnetic material 186 and around the middle of two strong magnetic materials 186. Thus, even when an external magnetic field changes, as shown in FIG. 4, the position in which the reproduction waveform 189 Of the vertical storage medium 183 is maximized can be matched with the position of the edge of the concavity and convexity of the substrate 185. Since in the above-described manufacturing method of a vertical storage medium, an external magnetic field is applied in the horizontal direction, the diamagnetic field generated inside the strong magnetic material 186 does not affect the vertical storage medium 183.
In the recent magnetic disk device provided with a high track-density magnetic disk (for example, hard disk device), servo information for controlling the operation of a magnetic head for reading/writing information from/into a magnetic disk is recorded in the magnetic disk. In this case, the quality of the reproduction waveform of the servo information can be improved by recording this servo information on the magnetic disk by the manufacturing method of a vertical storage medium to which an external magnetic field is applied in the horizontal direction as described above, thereby improving the reliability of the magnetic disk device.
Recently, with the improvement of the track density of a magnetic disk, in order to further improve the reproduction accuracy of the servo information, some magnetic disk device records eccentricity correction information for correcting the error of the servo information after recording the servo information on the magnetic disk. However, since this eccentricity correction information is usually recorded on the magnetic disk by a magnetic head, the reproduction waveform of the magnetic disk on which the eccentricity correction information is recorded forms a rectangular wave as shown in FIG. 5. Therefore, if in order to improve the track density of the magnetic disk while improving the quality of the reproduction waveform of the servo information, the eccentricity correction information is recorded by the magnetic head after recording the servo information on the magnetic disk by the above-described vertical storage medium manufacturing method of applying an external magnetic field in the horizontal direction, two types of read channels; one for reading servo information and the other for reading eccentricity correction information must be handled. If two types of read channels are handled, the configuration of the magnetic disk device becomes complex.
If an external magnetic field is generated using the electromagnet 190 shown in FIG. 6 in the above-described the vertical storage medium manufacturing method of applying an external magnetic field in the horizontal direction, one of the vertical storage medium 183 and the electro-magnet 190 must be relatively rotated against the other. In this case, it takes much time (tact time) to copy the servo information, compared with the case where an external magnetic field is applied in the vertical direction and the servo information is collectively copied to the vertical storage medium 183. The power supplied to the electro-magnet 190 increases for the longer copy time.
Patent reference 1: Japanese Patent Application Publication No. H10-40544
Patent reference 2: Japanese Patent Application Publication No. 2001-297433